Display screen portion with a transitional graphical user interface



FIG. 1 is a front view of a first image of a display screen portion witha transitional graphical user interface showing our new design;

FIG. 2 is a front view of a second image thereof; and,

FIG. 3 is a front view of a third image thereof.

The dashed broken line is for the purpose of showing portions of thegraphical user interface that form no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-3 . The process or period in whichone image transitions to another image forms no part of the claimeddesign.

CLAIM The ornamental design for a display screen portion with atransitional graphical user interface, as shown and described.